The proposed research will address the identification of acute HIV infections in ambulatory care medical settings in San Francisco. Many acutely HIV infected individuals seek medical care for symptoms of the acute retroviral syndrome, when they are highly infectious. Acute HIV infections diagnosed in medical settings would contribute both to earlier HIV case identification and opportunities to reduce HIV transmission. However, the real-world potential for acute case finding in ambulatory care medical settings is not known. Strategies for increasing symptoms-driven acute HIV diagnostic testing have also not been tested in this arena. We therefore propose to develop and evaluate the feasibility and acceptability of a novel health services intervention, specifically designed to increase the diagnosis of acute HIV infection by ambulatory care providers. The Acute HIV Testing in Ambulatory Care (ATAC) intervention addresses barriers that exist to performing acute HIV testing in the busy setting by: training and motivating providers to test, using both didactic training and an active social marketing strategy; introducing fast and simple algorithms for rapid acute HIV diagnosis; working with patients to promote acceptance of testing; and using a novel linkage support intervention to disclose positive results to patients and to coordinate linkage and follow-up of acute cases. Together, these components of the ATAC intervention aim to promote acute HIV testing, and to minimize the potential burden of testing on the providers, while ensuring that patients are rapidly linked to care and prevention services. In a 3 year project, we will accomplish three Specific Aims: First, we will fully develop, refine and operationalize the ATAC intervention. As interventions will involve new activities that will affect health department operations and patient care, intervention protocols for these activities will be pilot tested and refined based on feedback from these key stakeholders. Second, we will conduct a pilot study of the full ATAC intervention among 25 ambulatory care providers in a large public hospital ambulatory care clinic over a 1 year period, and measure the change in the total number of acute HIV cases identified under the ATAC intervention versus prior to the intervention. Finally, we will conduct a mixed methods process evaluation, eliciting feedback from participants and key informants on the feasibility acceptability and perceived value of specific intervention components. At the completion of the project, we will assess whether the pilot results indicate feasibility of the intervention: in this case a final intervention will be manualied for use in a citywide ATAC HIV prevention program, the efficacy of which would be evaluated in a larger intervention trial.